1. Field of Invention
The present invention relates to power systems, and more particularly, to a gate driver with short-circuit protection.
2. Description of Related Art
Power converters are essential for many modern electronic devices. Among other capabilities, power converters can adjust voltage level downward (buck converter) or adjust voltage level upward (boost converter). Power converters may also convert from alternating current (AC) power to direct current (DC) power, or vice versa. Power converters are typically implemented using one or more switching devices—such as, for example, metal-oxide-semiconductor field effect transistors (MOSFETs), insulated gate bipolar transistors (IGBTs), insulated gate field effect transistors (IGFETs), bipolar junction transistors (an's), etc.—which are turned on and off to deliver power to the output of the converter. Control circuitry is provided to regulate the turning on and off of the switching devices, and thus, these converters are known as “switching regulators” or “switching converters.” Such a power converter may be incorporated into or used to implement a power supply—i.e., a switching mode power supply (SMPS). The power converters may also include one or more capacitors or inductors for alternately storing and outputting energy.
The main function of any gate driver circuit is to convert a control signal to a power signal that can efficiently control the turn-on and turn-off of the switching device (e.g., IGBT or MOSFET). If the switching device requires short circuit protection, the gate drive circuit must safely turn-off the switching device during a shorted or abnormal overload condition. For example, it is common to use an IGBT for motor drive, uninterruptible power supply (UPS), or other industrial applications of power systems. The IGBT can be destroyed if it is turned-on into a faulted motor, an output short circuit, or an input bus voltage shoot-through. Under these fault conditions, current through the IGBT increases rapidly until it saturates. Because various fault conditions (e.g., short circuit) may occur during operation, fault protection should be employed to prevent the destruction of the IGBT.
There are several known techniques for turning off the IGBT once a fault condition is detected. These include discharging the gate of the IGBT through high gate resistance, abruptly reducing gate voltage to zero, adding source inductance to de-bias the gate, using a sense IGBT which senses fault current with a pilot cell, employing a gate voltage pattern analyzer for short-circuit protection in IGBT inverters, and using a current sense resistor or Hall-effect device to detect fault through the IGBT. None of these techniques are fully satisfactory.